FLAT-FIELD POSTOBJECTIVE POLYGON SCANNER

A general two-dimensional ray-trace analysis is presented for the moti on of a geometric focal point over a flat surface provided by a postob jective rotating polygon laser beam scanner. The exact defocus equatio n is derived for any value of the neutral scan position deflection ang le and the polygon rotation angle. The scan nonlinearity is derived fo r the special case of a zero neutral scan deflection angle. Geometric parameters were found that reduce the peak-to-peak defocus by more tha n an order of magnitude from that found in previous design approaches. Conditions were also found that reduce scan nonlinearity to less than 2 x 10(-4). Practical limitations, such as large polygons and beam ob scurations, encountered in the implementation of postobjective scannin g are discussed.